Aminoalkyl esters of 4-benzylpiperidine-1-carboxylic acid

ABSTRACT

THE INVENTION PROVIDES NOVEL AMINOALKYL ESTERS OF 4BENZYLPIPERIDINE-1-CARBOXYLIC ACID AND THEIR SALTS WHICH ARE USEFUL IN TREATING CARDIAC DISTURBANCES.

United States Patent (llfice 3,598,817 Patented Aug. 10, 1971 Int. Cl. C07d 29/24 US. Cl. 260-2471 34 Claims ABSTRACT OF THE DISCLOSURE The invention provides novel aminoalkyl esters of 4- benzylpiperidine-l-carboxylic acid and their salts which are useful in treating cardiac disturbances.

The present invention provides as new compounds, the 4-benzylpiperidine-l-carboxylic acid esters of the formula:

in which A represents a straight or branched alkylene chain, preferably of 2 to 8 carbon atoms, and R and R are the same or different and represent hydrogen or an alkyl or aralkyl radical, preferably alkyl of 1 to 4 carbon atoms or phenylalkyl in which the alkyl residue is of l to 4 carbon atoms, or together with the adjacent nitrogen make up a heterocyclic radical such as pyrrolidino, piperidino or morpholino, and the salts of these basic esters with pharmaceutically acceptable acids, such as hydrochloric, ascorbic, maleic or succinic acid, and especially hydroxy-acids such as tartaric, citric, lactic or hydroxymaleic acid.

According to the invention, the compounds of Formula I and their pharmaceutically acceptable acid addition salts are prepared by reacting an amino-alcohol of formula:

in which A, R and R are as hereinbefore defined, with a halide or an alkyl ester of 4-benzylpiperidine-l-carboxylic acid, and optionally converting a base so obtained into a pharmaceutically acceptable acid addition salt. The reaction preferably takes place in the presence of a basic condensation agent.

According to a further feature of the invention, the compounds of Formula I and their pharmaceutically acceptable acid addition salts are prepared by reacting 4- benzylpiperidine with a halogenoformate of the formula:

XCOOA--Z in which X is a halogen atom, Z is a halogen atom or a radical of formula and A, R and R are as hereinbefore defined, followed, where Z is halogen, by reaction of the product with an amine of formula HNRR', and optionally converting a base so obtained into a pharmaceutically acceptable acid addition salt thereof.

These methods of preparation are shown schematically below:

First process (R"-lower alky-l) Second process Method C:

Method D:

The detailed operation of methods A, B, and C is described in the examples below.

The salts of the compounds of Formula I are obtained by separately dissolving the basic ester and the desired acid in an alcohol and mixing the two solutions. The salts generally precipitate at least partially. It is possible to separate them by adding diethyl ether and/or by evaporating the solution. For example, to obtain the citrate of the fl-diethylaminoethyl ester of 4-benzylpiperidine-lcarboxylic acid, the basic ester and the citric acid are separately dissolved in an alcohol, in particular isopropanol, and the two solutions are then mixed. The salt precipitates partially. It may be separated by adding diethyl ether. After standing, the crystalline compound is filtered off, washed with diethyl ether, and dried.

The following non-limiting examples illustrate the invention. Temperatures are in degrees centigrade.

EXAMPLE 1 fl-Diethylaminoethyl 4-benzylpiperidine-l-carboxylate and its citrate (a) The acid chloride of benzylpiperidine-l-carboxylic acid is prepared in the following manner. 50 g. of 4- benzylpiperidine (0.28 mol) are added dropwise to a 20% strength solution of 72 g. (0.14 mol) of phosgene in toluene, at a temperature of about 0. After completion of the addition, the mixture is allowed to return to ordinary temperature and the precipitated benzylpiperidine hydrochloride is filtered off. The filtrate is evaporated to dryness. 31 g. (93% yield) of the acid chloride are obtained and are used without purification for conversion to the ester.

(b) 3.45 g. of sodium are added to 17.8 g. of fi-diethylaminoethanol (0.15 mol) in 200 m1. of anhydrous toluene, and the mixture is heated under reflux until all the sodium has dissolved. 31 g. (0.13 mol) of the acid chloride previously obtained, dissolved in ml. of toluene, are

then added dropwise. Reflux is continued for 2 hours. The reaction mixture is taken up in Water, and the toluene layer is separated and dried. The resulting residue is distilled under reduced pressure after the solvent has been evap- The aminoalcohol is converted into its citrate, which is hygroscopic and very soluble in water, by the standard procedure.

EXAMPLE 3 orated. 27 g. of an oil of a pale yellow colour (66% yield), 5 boiling at about 170-175 under a pressure of 0.1 mm. of p zgiiggfig gzfig 31 32 12233??? 1 mercury, are thus obtained. Amine determination: calculated molecular weight, 317; equivalent found, 317.2. of Sodium ((107 8- atom) are heated l (c) Reaction of citric acid with the amine in equimolec- I6fi1lX t a Solution of 24 of l ular proportion yields a monocitrate which crystallises 10 pfopylamlnoethaQolin1 50m1-oftollleneuntllcompletPly Well and which is purified by reprecipitation in a mixture dlssolved- The mlxtul'e l5 cooled to 9 and a solufiqn of alcohol and diethyl ether. The citrate melts at about 0f H101) 0f y p p y 110 (decomposition). Its solubility in water i mo than acid chloride in 100 ml. of toluene 1s added all at once. 15% and the Saturated Solution h a PH of b t 5 The mixture is boiled for 8 hours. After cooling, 200 ml. 15 of water are added. The organic layer is extracted with EXAMPLE 2 dilute hydrochloric acid. The aqueous phase is rendered alkaline and then extracted with diethyl ether. The extract l'NNdlethylammciprop'zyl 4'benzylp 1p endmecar' is dried and fractionated. 13.7 g. of the desired basic ate an curate ester, a yield of 62%, are obtained, B.P. 17s/o.01 mm. (a) Ethyl 4-benzylpiperidine-l-carboxyl i p p 20 Hg. Analysis: (amine determination) molecular weight as follows. 16.3 g. of ethyl chloroformate (0.15 mol) are calculated, 347; molecular weight found, 343. added dropwise to a well-dried 3-necked flask containing (b) The amine is converted into the hydrochloride with 26.1 g. of 4-benzylpiperidine (0.15 mol), 100 ml. of pyrihydrogen chloride in ethanol solution. The hydrochloride i e and 0 f benzene, With cooling in a a of c melts at 115. Analysis: inorganic Cl, percent calculated, and salt. The mixture is stirred for 1 hour at ambient 05 9.47; found, 9.47. The solubility of this salt in water is temperature and then for 2 hours with heating under reover 20%. flux. The resulting precipitate is filtered off and the filtrate Other compounds corresponding to general Formula I is evaporated to dryness to drive off the excess pyridine. were prepared in an entirely similar manner and in ac- The residue is taken up in diethyl ether and the ethereal cordance with the techniques described in Examples 2 and extract is washed with water and then with dilute hydro- 3. The only differences are in the heating time, which is chloric acid. After neutralisation with sodium bicarbonate longer or shorter depending on the reactivity of the startand drying, the ethereal extract is fractionated. 30 g. of ing materials. Sodium may be replaced as the condensathe desired ester, representing a yield of 81%, are obtion agent by another alkali metal such as potassium or tained (boiling point: 140/ 0.03 mm. Hg). Determination by an alkaline earth metal such as magnesium. Other inert of nitrogen: N percent calculated, 5.66; N percent found, solvents, such as benzene or xylene, may be used. 5.73. The yields are good (5075%) and the analytical re- (b) 12.3 g. of ethyl 4-benzylpiperidine-l-carboxylate sults satisfactory in the case of all the derivatives. Table I (0.05 mol) and 20 g. of 1-N,N-diethylaminopropanol-Z gives a first list of products obtained (including those of (0.15 mol) are mixed in a distillation flask. The mixture Examples 1, 2 and 3) with their characteristics. is heated to about 150 and 0.3 g. of sodium is added in Before this, the preparation of another intermediate, small pieces. The mixture is heated for 30 minutes at 150 namely methyl 4-benzylpiperidine-l-carboxylate, will be and the temperature progressively raised to drive off the described. 18 g. of 4-benzylpiperidine-l-carboxylic acid ethanol formed and the excess aminoalcohol. After coolchloride (0.076 mol) are added a little at a time to a ing, the mixture is taken up in dilute hydrochloric acid solution of 1.8 g. of sodium (0.078 g. atom) in 150 ml. and extracted with diethyl ether. The aqueous layer is of methanol. The mixture is kept at about for 2 hours, rendered alkaline and then extracted again with diethyl fi t r d, taken up in Water and then extracted with diethyl ether. The ethereal solutions are combined, repeatedly ether. The ethereal extract is dried and then distilled. washed with water, dried, and fractionated. 8 g. of prod- 13.8 g. of the desired ester, a yield of 77% (B.P. l40l/ uct, a yield of 50%, are obtained, B.P. 185/ 0.07 .mm. Hg 0.05 mm. Hg) are obtained. or 170/0.05 mm. Hg. 50 The various other lower alkyl 4-benzylpiperidine-1- Analysis.Amine determination, molecular weightcalcarboxylates y also be P p as described above culated, 332; molecular Weight found, 333. and in (a) of Example 2.

TABLE I i M 3213?. the hydro- Example chloride, No. .R .R R Boiling point of the amine degrees 1 I -CH2CH2 C2H5 DgHs l175/0.1I11II1 2 CHCH2 Same Same as above l70/0.05 mm. Hg

3 CH2-CHzlC H llC H7 178/0.01 mm. Hg

4 -(|3HCH2 CH3 EH3 146-8/0.001mm. Hg 114 5 (|-JH--CHz- 02115 132115 18U/0.05 111111. Hg

C3H7n 6 CH2CH2- in-C4Hg l'l-U H9 l95200/0.05 mm. Hg

18O/0.05 mm. Hg

7 Same as above y -Iii 8 d0 CH; L3H; l52/0.01m1n. Hg

TAB LE IContinued R Melting point of N the hydro- Example chloride, No. A R R R Boiling point of the amine degrees 1 9...- do N/ \O 210/0.05 mm. Hg 1 162 1U PH; C2115 02H: Approx: 210/0.02 mm. Hg 129 11 $H; H H 22030/0.001 mm. Hg

-'C GH2 CH3 CH2('3H CH3 CH2 12 CHzCHz- CH3.. CH2CHz-C&H5 220/0.03 mm. Hg

13 -CHOH Same Same as above 250/0.03 mm, Hg 1 l4 Same as above do i-G3H7 170/0.0i mm. Hg 15 2GH2CHz C2H5 C2H5 1905/0.05 mm. Hg 86 1 Decomposition.

EXAMPLES 16 TO 28 2-(N,Ndi-n-butylamino)-propyl 4-benzylpiperidinol-carboxylate The starting 1-chloro-2-propanol,

C1CH CHOHCH is obtained by the method of Dewael, Bull. Soc. Chim. Belges 39, 87-90 (1930). This halogeno-alcohol is con verted into l-chloroisopropyl chloroformate in the following manner: 130 g. of phosgene are passed into a stirred solution of 1 mol. (95 g.) of 1-chl0ro-2-propanol in 350 ml. of toluene at 0. The mixture is allowed to return to ordinary temperature while stirring is continued. After 12 hours standing the excess phosgene is removed by a stream of nitrogen and the toluene is evaporated. The residue is distilled. The fraction (52 g.) which passes over at 147-160/760 mm. Hg is collected. This product is not purified for the next stage.

A solution of 37 g. of the above compound in 100 ml. of dry diethyl ether is then added dropwise and with gentle cooling to a solution of 0.4 mol (69.6 g.) of 4-benzylpiperidine in 100 ml. of dry diethyl ether. When the addition is complete, stirring is continued and the mixture then kept under reflux for 1 hour and allowed to stand for 12 hours. A precipitate of 4-benzylpiperidine hydrochloride forms and this is filtered off and washed with 200 m. of diethyl ether. The combined ethereal solutions are washed, first with 80 m1. of water+l0 ml. of concentrated hydrochloric acid, then with 80 ml. of water, and finally with 40 ml. of water. They are then dried over anhydrous magnesium sulphate, the ether is evaporated, and the residue is distilled. 41 g. of 1-chloro-2-propy1 4-benzylpiperidine-l-carboxylate, a yield of are obtained, B.P. about 185/0.02 mm. Hg. Analysis of Cl: theoretical, 12.02%; found, 12.0%.

The compound is finally converted into the desired product in the following manner. A mixture of 17.6 g. (0.06 mol) of 1-chloro-2-pr0pyl 4-benzylpiperidine-1-carboxylate, 50 ml. of di-n-butylamine (0.3 mol) and about 0.5 g. of sodium iodide is kept under reflux for 12 hours in an oil bath at 160. The whole is then taken up in 300 ml. of diethyl ether. After the dibutylamine hydrochloride has been separated, the ethereal liquid is twice extracted with dilute hydrochloric acid. The hydrochloric acid solution is rendered alkaline with 10 N sodium hydroxide solution with cooling, and the aqueous phase is subjected to four successive extractions with ml. of diethyl ether each time. Finally the ethereal solution is dried, the solvent is evaporated, and the residue is fractionated. 8.5 g. of the desired product, a yield of 37%, are thus ob tained, B.P. 200-210/0.03 mm. Hg. n =1.S045. Amine analysis: molecular weight calculated, 387; found 382.

Table II is a list of products obtained with the method of preparation used for each of them, the yields and the characteristics of these products.

TABLE II Melting point of the hydro- Yleld, chloride, Example No. A R R Method percent Boiling point of the amine degrees 16 -([3HCH2 -C H n -C4H9l'i G 37 210/0.03 mm. Hg

17 CH2-OH -O H n C H n A 18--- Same as above. CH CH2C H5 A 19- do C2H5 -CH2CHzCeH A 20 do O H1n Same as above. A 21 -do GH (CH2) C H5 A 22 -CHCH- G H1i C H i A 40 180/0.06 mm.Hg 132 23 Same as above C H n C3H1n A 35 190/0.02 mm. Hg 24 do -OH -CH C5H A 52 225/0.03 mm. Hg

25 -CHCH C H5 O H A 63 180/0.05 mm. Hg

TAB LE 11- Continued Melting point of the hydro- Yield, chloride,

Example No. A R It Method percent Boiling point of the amine degrees 26 (CH2) CH3 ll3H3 1B 63 182-182.5/0.05 mm. Hg 150 27 (CH?) 0. H1n ll;il'I1n 113 51 200/0.07 mm. Hg

28 CH-CH CH2 C;Ha ./;1H5 it 37 162/0.04 mm. Hg

Of source each of the products identified in Tables 1 and II can be prepared by any of the methods A to D.

The new compounds were subjected to a series of pharmacological examinations. They were for the most part tested in the form of the base dissolved in aqueous citric acid immediately before use. The doses mentioned are expressed as the base.

The pharmacological techniques are presented below as applied to the product of Example 1.

Acute toxicity The experiments were carried out on male mice of Swiss strain, of weight varying from 18 to 20 g. The 50% lethal doses were calculated by the method of Miller and Tainter (Proc. Soc. Exp. Biol. Med, 1944, 57, 261).

The following results were found for the compound of Example 1:

LD administered intravenously: 48:2 mg./kg. LD administered intraperitoneally: about 125 mg./kg. LD administered orally: 400:20 mg./kg.

Anti-fibrillating activity (a) Stimulation of the isolated rabbit auricle.The method of Dawes, as modified by Alles and Ellis (Ann. N.Y. Acad. Sciences, 1956, 64, 552), was used This technique makes it possible to study the effect of a compound during the refractory period of the heart. An isolated rabbit auricle, dipped into Ringer-Loubatieres liquid, is electrically stimulated at increasing frequency until a phenomenon of missing-out (2:1 rhythm in place of 1:1 rhythm) is observed. In the presence of an anti-fibrillating agent the desynchronisation appears at a lower frequency (extension of the refractory period). The reference substances are procainamide and quinidine. The results are expressed as a percentage reduction of the maximum missing-out frequency.

Citrate of fl-diethylaminoethyl 4-benzylpiperidine-l-carboxylate:

1 ,Llg-/II]]. of bath% 2 g/ml. of bath2l% 5 ig/ml. of bath-28% Procainamide:

10 ig/ml. of bath6% 20 ug/ml. of bath-10% Quinidine:

5 ugJml. of bath16% 10 ug/ml. of bath24% (b) Intravenous injection of ouabaine into dogs-A technique based on that of Arnaud et al. (CR. Soc. Biol. 1965, 159, 2427) was used. A male or female adult mongrel dog is given an intraperitoneal anaesthetising injection of mg./kg. of pentobarbital and an intravenous injection of atropine (1 mg./kg.). An initial dose of 40 ig/kg. of ouabaine is then injected into the dog by the same route, followed 30 minutes later by a dose of 10 ,ugJkg. of the same product followed every 10 minutes by fresh administrations of ouabaine at a dose of 10 ,ug/kg. until cardiac disturbances are set up which are examined by an electrocardiogram (derivations D II and D III) asd which comprises extrasystoles, ventricular tachycardia, and

minute a few infrequent extrasystoles reappear in groups (salvos) but the graph remains stabilised for at least minutes.

Procainamide at an intravenous dose of 10 mg./kg. of the LD causes a slight and transient improvement in the rhythm and in the electrocardiograph, with disturbances re-occurring within 5 minutes following the injection.

Quinidine at an intravenous dose of 7 mg./ kg. of the LD renders the rhythm regular after 4 minutes, with the electrocardiograph anomalies being preserved and with arhythmia returning 20 minutes after the injection.

(c) Ligature of the coronary artery in dogs.The experiments were carried out by the method of Harris et al. (Circulation Res. 1950, 1, 13; 1951, 4, 522). A male or female adult mongrel dog weighing between 10 and 15 kg. is anaesthetised with pentobarbital (15 mg./kg., administered intraperitoneally) and subjected to artifiical respiration. The dog is placed in the lateral decubitus position and its thorax is opened at the level of the 4th left intercostal space. A pericardial bed is introduced, the descending branch of the left coronary artery is detached between the 2 first collaterals visible after the auricle, and constriction thereof is caused by ligature around a mm. mandrel which is introduced against the artery and then withdrawn. After 30 minutes, total constriction of the artery is brought about by a second ligature. The thorax of the animal is then again closed and the dog is re-animated. After 24 hours. a ventrical arhythm which is compatible with survival of the animal manifests itself. The animal is then treated with the anti-fibrillating product being studied and its electrocardiogram is followed (derivations D II and D III). The salvos of ventricular extrasystoles are counted during reference periods of 10 minutes. The citrate of the compound of Example 1 is compared with the procainamide and quinidine.

The citrate, administered intravenously at a dose of 5 mg./kg., causes a clear reduction in the number of extrasystoles, during the 10 minutes following its injection, relative to the average observed over the course of several 10 minute periods preceding its administration.

Procainamide at an intravenous dose of 10 mg./ kg. only causes a veryslight diminution in the number of extrasystoles, whilst quinidine at an intravenous dose of 7 mg./ kg. allows a more marked effect to be observed during the first 10 minutes.

In conclusion, this series of experiments establishes that the new basic ester has a greater anti-arhythmic activity than either rocainamide or quinidine.

Effect on blood pressure This effect was investigated on anaesthetised rats and dogs. After liberating the carotid, a cannula is introduced into it and the pressure is recorded by a Condon monometer (Brit. J. Pharmacol, 1951, 6, 19). The effect of the compound under test on the initial pressure and on the response to various stimuli is studied.

10 In rats, at an intravenous dose of 2 to 5 mg./lrg., the Anti-fibrillating eflect citrate of the compound of Example 1 causes a brief and (a) Stimulation of the isolated amide of the rabbit.

slight hypotension without modifying the reactions to adrenalin, to nicotine and to stimulations of the central The results are collected m Table and peripheral nerve X. 5 TABLE Iv In dogs, at an intravenous dose of 5 mg./kg., the com- P t pound produces a moderate hypotension which is relatively P d f igif f prolonged. The effect of acetylcholine appears to be slightly m net Dose in E ema immn increased but those of adrenalin and histamine remain fifi gr iigi ii c ii ii y Notes unchanged. Spasmolytic activity in vitro g :3? The standard Magnus technique was used (Pfliigers i :52 Arch. 1904, 102, 123). A value of about ug/ml. is 2.5 28 found for the 50% effective spasmolytic dose on the iso- 1 ffigi g fi bonded lated guinea pig ileum stimulated by histamine [Prometh- 5 azine is effective at a concentration of 0.05 ,ug./ml.]. 2 fig In the case of the isolated duodenum of a rat, contracted 0 25 by the action of BaCI this ED is 10 ,ug./ ml. [Papaverine i is equally effective at a concentration of 5 g./ml.]. 2.2 Local anaesthetic effect The disappearance of the oculo-palpebral reflex caused If; Do, by a fine hair was investigated in rabbits by the method of 14 Rgnier (CR. Acad. Sciences 1923, 558) after instilling a 5 solution of a local anaesthetic (evaluation of the surface 15 jg anaesthetic elfect). The compounds are tested as a 1% n 2.5 27 solution in water and are administered in a volume of 16 :g ml. The citrate of the compound of Example 1 has 0,5 -e an activity which is about half that of cocaine hydrof chloride. 2.5 23

The depth local anaesthetic effect was observed by the 19 g :5; technique of Moukhtar, modified by Bulbring and Wajda The solilbility is lllfldeqiltte ll'fil thisdtestto ganedi out (J. Pharmacol. 1945, 85, 78). The disappearance of the P 1 0 skin reflex following stimulation of the dorsal skin of the hows mm mm guinea pig (vaccinostyle) is investigated after intradermic Ii: injection of the anaesthetic solution (0.5% strength solu- 1 25 dose tion, 0.2 ml. volume). The new compound exerts an effect 25 Toxic efiw't on the amide which is close to that of procaine hydrochloride. 0.5 16

The compounds of Examples 2 to 28 were subjected to 40 g 5 a series of pharmacological examinations in accordance 1 20 h dose with the techniques set out above. The products of Ex- '14 amples 2 and 8 were used as the citrates, of Examples 3,

4, 7, 9, 10 and 15 as the hydrochloride, and of Examples 5, 6, 11-14 and 16-28 as the bases dissolved in aqueous citric acid solution. In this last case the doses employed are expressed as the base.

(b) Intravenous injection of ouabaine into dogs. The results, collected in Table V, are expressed in the following manner:

Acute toxicity total and definitive protection 'from the first The results are shown in Table III. lnlecllon Onwardstotal and definitive protection after a few in ec- TABLE III Hons partial protection. L135, lg/kg regularisation of the rhythm without normalisation Adminisof the complexes. Produetof Adminis- Administered teredintra- Example No. tered orally intravenously peritoneally TABLEV 2 350 Product of Dose,

Example No. mg./kg. Protection Notes 2 M0 of the LDsu. 15 minutes after a single injection the trace is normal and the protection lasts at least 90 1 Administered intravenously by injection.

(c) Ligature of the coronary artery in dogs. The administrations of the product are repeated every 1% hours. The results are collected in Table VI.

TABLE VI Iroduct of Dose admin- Method of Example N0. lstered,mg./kg. administration Results 2 g 100 Oral Almost total protection [or 21 hours after the 2d ingestion. 100 do Different animal. 70% protection after the 3rd ingestion. 3 50 Oral Total protection for a period of 24 hours after the 3rd ingestion. After 48 hours the arhythms reappear and a 4th dose causes a definitive protection. 4 4. 3 I.v Marked antiarhytlimic efiect without complete disappearance of the disturbances. 5 130 Oral Approximately 50% protection after 2d ingestion.

130 do Marked efiect on the 3rd ingestion. Protection of the order of 40 to 80%. 50 .do Partial protection at the 2d ingestion (with convulsionsl. Total protection in 15 minutes lasting Ior at least 6 hours. tio Partial protection alter the 1st administration, becoming hours.

complete at the 2d administration. Duration more than 7 (d) Auricular arhythm induced in rats by aconitine. A modification of the method of Scherf (Proc. Soc. Exp. Biol. Med. 1947, 64, 233) was used. Adult rats of the Wistar strain and weighing between 150 and 200 g. are anaesthetised by injection of 1 g./kg. of ethyl earbamate and placed under artificial respiration. A cannula intended for the administration of anti-arhythmic products is introduced into the femoral vein. The electrocardiogram is recorded on derivations D II and D III. A catheter is introduced into the right jugular vein of the rat so as to reach the auricle. The products to be tested are administered into the femoral vein in a volume of 0.2 ml. per 100 g. of animal weight. One minute later 7.5 ,ug. of aconitine nitrate in a volume of 0.1 ml. are injected through the jugular catheter. In the absence of an anti-arhythmic efiect the disturbances which are characteristic of auricle fibrillation manifest themselves in 3 minutes following the injection and have an average duration of 30 minutes. If on the other hand the product being tested is active, at more or less extended protection against these disturbances is observed.

A scale with the following ratings was used.

Duration of protection: Rating Less than 5 minutes l) 5 to 9 minutes l 10 to 14 minutes 15 to 29 minutes 3 Greater than 30 minutes 4 Since the experiments were carried out on batches of 5 rats, a rating of is obtained with total protection. The results are collected in Table VII.

TABLE VII Product of Dose, Total Example N o. mg./kg. rating Notes 27 l6 E6 of the LD 14 I4 34 of the LD 12 16 M of the LD 8 7 Of the LD5U. 22 V of the LDw. 16 5 Do. 10 4 Do. 22 1 Do. 40 5 Do. 40 l) Do. 16 1 .Do. 16 3 Do. 14 t) .130. 12 t] Do. 11 5 Do. 12 0 Do.

4 i1 0f the LD50. 7 l3 .46 of the LDsu. 12 M of the LD l1 0 Do. 17. 5 IlDo.

Insoluble compound 17 l) of the LD50; the animal dies a few minutes after the injection iii it is not under artificial respiration. 4. 5 l) 144 of the LD50. 6 .30 oi the LDsu 4 17 M of the LD;, 7 (2) 0f the LDsu 11 I) M ol the LD TABLE VII.Continued Product of Dos Total Example N o. tug/kg 1 rating Notes 17 of the LDso; the animals die a few minutes after injection of the product. 10 l oi the LDsu. 718 0 Do. 6 ltr D0. 7 5 16 DO.

1 Administerd intravenously. 2 Toxic etiect.

EflFect on blood pressure Experiments were carried out with rats using the technique described above. All the products of Examples 2 to 15 produce slight hypotensive effects at doses of 1.2 and 5 mg./kg. An increase in the efiects of adrenalin is generally observed, but the effects of acetylcholine are unaltered.

The majority of the products of Examples 16 to 28 administered intravenously at doses of 1 to 5 mg./kg. are transient hypotensive agents of average intensity which do not cause changes in the effects of adrenalin and acetylcholine. The following exceptions were however observed. The product of Example 19 has a more prolonged hypotensive effect at an intravenous dose of 5 mg./ kg. with an increase in the effects of adrenalin and a reduction in those of acetylcholine. The product of Example 22 has a moderate hypotensive eifect with a slight adrenolytic effect. The product of Example 27 has a slight hypotensive eflect with an increase in the action of adrenalin at an intravenous dose of 5 mg./ kg.

spasmolytic activity in vitro The standard method of Magnus was used. All the products show a musculotropic spasmolytic eifect ranging from half to six times that of papaverine. The most active compounds amongst those of Examples 2 to 15 are, in order of decreasing activity, those of Examples 14, 15, 12 and 2.

The products of Examples 16 to 28 in turn generally show a strong spasmolytic musculotropic activity comparable with that of papaverine. The results are shown in Table VIII.

Analgesic efiect The method Siegmund (Proc. Soc. Exp. Biol. Med. 1957 95, 729) was used. The intraperitoneal injection of 2-phenyl-l,4-benzoquinone causes a particular syndrome in mice which is characterised by intermittent contractions of the abdomen, a twisting of the trunk and an extension of the rear paws. Narcotic and non-narcotic analgesics are antagonistic to this syndrome. The percentage of protection 20 minutes after oral administration of the products is investigated, with acetylsalicylic acid serving as a reference compound.

All the compounds of the invention show a slight analgesic eifect which, in the majority of cases, is less than that shown by the same dose of acetylsalicylic acid. The most active products are those of Examples 12 and 7. They respectively give 66 and 58% protection, while in the same dosage, acetylsalicylic acid only gives protection of 46%.

The new esters of the Formula I and their pharmaceutically acceptable acid addition salts may be used as medicines in the clinical treatment of human beings, in disturbances of the cardiac rhythm and in particular in palpitations, auricular and ventricular extrasystoles, fibrillation and flutter, auricular tachysystoles, paroxystic tachycardia, rhythm disturbances following treatment by digitalis-type materials and rhythm disturbances observed in cases of myocardial infarction. They can be administered parenterally, orally or rectally.

The invention accordingly includes within its scope pharmaceutical compositions comprising in association with a pharmaceutically acceptable carrier or coating, a 4-benzyl-1-piperidine carboxylic acid ester of Formula I or a pharmaceutically acceptable acid addition salt thereof.

The following examples illustrate such pharmaceutical compositions.

Injecta-ble solution for subcutaneous, intramuscular or intravenous injection Citrate of the compound of Example 1 or of that of Example 22: 0.020 g. Sterile isotonic saline, q.s. for an ampoule of 1 ml.

or Citrate of the compound of Example 2: 0.010 g. Sterile isotonic saline, q.s. for an ampoule of 1 ml.

The ampoules can also be of 2 or 5 ml. and the amount of active principle can vary from 0.01 to 0.1 g./ml.

Tablets G. Citrate of the compound of Example 1 or hydrochloride of the compound of Example 3 005 Rice starch 0.07

Talc 0.10 Magnesium stearate 0.003

These tablets may be coated or turned into dragees. The content of active principle may range from 0.02 to 0.10 g. per tablet for the compound of Example 1, or from 0.02 to 0.15 g. for that of Example 3, and any of the usual excipients for this pharmaceutical form may be used.

Further example of tablets G. Hydrochloride of the compound of Example 22 0.075

Rice starch 0.07 Talc 0.10 Magnesium stearate 0.003

Imhausen excipient, q.s.p.: 1 suppository The dose of active principle may be up to 0.25 g. for the compound of Example 1, 0.30 g. for that of Example 5 and 0.50 g. for that of Example 22. The other usual eXcipients such as cacao butter may be used.

The new compounds may be administered at average daily doses of to 500 mg. orally or rectally or 50 to 200 mg. parenterally.

The various basic esters and their salts may of course be present in the pharmaceutical compositions either alone or combined with one another, or with other active principles.

We claim:

1. A 4-benZylpiperidine-1-carboxylic acid ester of the formula:

and its pharmaceutically acceptable acid addition salts, in which A is a straight or branched alkylene chain of 2 to 8 carbon atoms, R is alkyl of 1 to 4 carbon atoms, R is alkyl of 1 to 4 carbon atoms or phenylalkyl in which the alkyl residue is of 1 to 4 carbon atoms, or R and R together with the adjacent nitrogen make up a pyrrolidino, piperidino or morpholino group.

2. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the Z-diethylaminoethyl ester of said 4-benzylpiperidine-l-carboxylic acid.

3. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the Z-diethylamino-l-methylethyl ester of said 4-benzylpiperidine-l-carboxylic acid.

4. A 4-benzylpiperidine-l-carboxylic ester according to to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the 2-diisopropylaminoethyl ester of said 4-benzylpiperidine-l-carboxylic acid.

5. A 4-benzylpiperidine-1-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the 2-dimethylamino-1- methyl-ethyl ester of said 4-benzylpiperidine-l-carboxylic acid.

6. A 4-benZylpiperidine-1-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the l-diethylaminomethyln-butyl ester of said 4-benzylpiperidine-l-carboxylic acid.

7. A 4-benzylpiperidine-1-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the 2-(di-n-butylamino)ethyl ester of said 4-benzylpipen'dine-l-carboxylic acid.

8. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts wherein said ester is the 2-piperidino(1)ethyl ester of said 4benzylpiperidine-l-carboxylic acid.

9. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the Z-dimethylaminoethyl ester of said 4-benzylpiperidine-l-carboxylic acid.

10. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the 2-morpholino(4)ethyl ester of said 4-benzylpiperidine-l-carboxylic acid.

11. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the 2-diethylamino-1,l-dimethylethyl ester of said 4-benzlypiperidine-l-carboxylic acid.

12. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the 5-amino-1,1,5-trimethylpentyl ester of said 4-benzylpiperidine-l-carboxylic acid.

13. A 4-benzylpiperidine-1-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the Z-(N-methyl-N-phenethylamino)ethyl ester of said 4-benzylpiperidine-l-carboxylic acid.

14. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the Z-(N-phenethyl-N-methylamino)-1-methyl-ethyl ester of said 4-benzylpiperidine-lcarboxylic acid.

15. A 4-benzlypiperidine-l-carboxylic ester according to claim 1 and its harmaceutically acceptable acid addition salts, wherein said ester is the Z-(N-isopropyl-N-methylamino)-1-methyl-ethyl ester of said 4-benzylpiperidine-1- carboxylic acid.

16. A 4-benzylpiperidinel-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the 3-diethylaminopropyl ester of said 4-benzylpiperidine-l-carboxylic acid.

17. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the 2-(N,N-di-n-propylamino) ethyl ester of said 4-benzylpiperidine-l-carboxylic acid.

18. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the Z-(N-methyl-n-benzylamino)ethyl ester of said 4-benzylpiperidine-lcarboxylic acid.

19. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the Z-(N-ethyl-N-phenethylamino)ethyl ester of said 4-benzylpiperidine -l-carboxylic acid.

20. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the 2-(N-n-propyl-N-phenethylamin)ethyl ester of said 4-benzylpiperidine-l-carb0xylic acid.

21. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the 2-(N-methyl-N-phenylpropylamino)ethyl ester of said 4-benzylpiperidine-l-carboxylic acid.

22. A 4-benzylpiperidinel-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts wherein said ester is the l-(N,N-di-n-propylamino) progyl-(Z) ester of said 4-benzylpiperidine-l-carboxylic aci 23. A 4-benzylpiperidinel-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the l-(N,N-dipropylamno) P PW ester of id 4- cnzylpiperidine-l-carboxylic aci 24. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the l-(N,N-di-n-butylamino) p f gy ester of said 4-benzylpiperidine-l-carboxylic aci 25. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the l-(N-methyl-N-benzylamino)propyl-(2) ester of said 4-benzylpiperidine -1-carboxylic acid.

26. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the 1-(N,N-diethylamino) butyl-(Z) ester of said 4-benzylpiperidine-1-carboxylic acid.

27. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the 1-(N,N-dimethylamino) propyl-(3) ester of said 4-benzylpiperidine-1-carboxylic acid.

28. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the 1-(N,N-di-n-propylamin o) propyl-(3) ester of said 4-benzylpiperidine-1-carboxylic acid.

29. A 4-benzylpiperidine-l-carboxylic ester according to claim 1 and its pharmaceutically acceptable acid addition salts, wherein said ester is the 1-(N,N-diethylamino) butyl-(3) ester of said 4-benzylpiperidine-l-carboxylic acid.

30. 2-(N,N-diethylamino)ethyl 4 benzylpiperidine-lcarboxylate and its pharmaceutically acceptable acid addition salts.

31. l-(N,N-diethylamino)-2-propyl 4-benzylpiperidinel-carboxylate and its pharmaceutically acceptable acid addition salts.

32. 1-(N,N-diisopropylamino)-2-propyl 4 benzylpiperidine-l-carboxylate and its pharmaceutically acceptable acid addition salts.

33. 2- (N,N-diisopropylamino)ethyl 4-benzylpiperidinel-carboxylate.

34. l- N,N-diethylamino -2-pentyl 4-benzylpineridinel-carboxylate.

References Cited UNITED STATES PATENTS 3/1936 Rider 260-43 6/1957 Cusic 260326.3

HENRY R. JILES, Primary Examiner G. T. TODD, Assistant Examiner U.S. Cl. X.R. 

